Biogas conversion to liquid fuels via chemical looping single reactor system with CO2 utilization

Abstract

AbstractThe chemical looping single reactor (CLSR) system utilizing calcium ferrite as oxygen carriers represents an innovative approach to biogas reforming, which has the potential to enhance the efficiency and sustainability of biogas production. In this process, an oxy-combustion burner supplies the necessary endothermic heat while CO2 is simultaneously utilized, resulting in an autothermal process that generates high-purity syngas. Nearly 20% higher CO2 utilization can be achieved compared to the tri-reforming, owing to the higher driving force for CO2 oxidation in the counter-current moving bed and steam knock-out before inletting the flue gas into the reactor bottom. Additionally, the CLSR system is robust to variations in biogas to oxygen carrier ratios and CO2 concentration of the inlet feedstock, maintaining the outlet syngas purity within 1% variation. The effects of temperature, pressure, heat integration, and additional H2O/CO2 flow rate on the system performance are discussed, and the optimized scenarios are used for liquid fuel generation. The proposed process achieves about 13% reduction in syngas requirement compared to the conventional tri-reforming for the same amount of liquid fuel production. The feasibility of the CLSR system is further experimentally verified under various conditions. The results reveal the occurrence of CO2 counter-oxidation reactions on the surface of calcium ferrite oxygen carriers and demonstrate that higher temperatures are beneficial for the CH4 reforming reaction.